10 CYCADALES [CH. 



Sir Joseph Hooker^ speaks of Cycas living in the deepest and 

 hottest valleys in Sikkim. Encephalartos is essentially a xero- 

 philous genus. Stangeria paradoxa is said to be confined to forests 

 in Cape Colony, and another species grows among the grass of 

 the Park-lands in open country^. While it is true that many 

 Cycads are characteristic of dry regions some species flourish 

 in places where shade and moisture are abundant. 



Though it is impossible in many cases to form an estimate 

 of the age of individual plants, there are clear indications that 

 some specimens afiord notable instances of longevity. Chamber- 

 lain estimates the age of some plants of Dioon spinulosum as 

 exceeding 400 years and mentions an example of D. edule that 

 is probably 1000 years old. An unusually tall plant of Encephalar- 

 tos in the Botanic Garden of Amsterdam is believed by Prof, de 

 Vries to have reached the venerable age of 2000 years^. The 

 restricted range and in many cases the solitary existence of recent 

 Cycads, with their tall stems clothed with the persistent cork- 

 covered stumps of thousands of fronds, deepens the impression 

 of antiquity derived from a study of the geological history of 

 this dwindhng race. 



Stems. The tall columnar stems of some species of Cycas, 

 often branched or bearing numerous ovoid buds like enlarged 

 bulbils*, are characterised by the regular alternation of large and 

 small leaf-bases as seen in the stem of C. circinalis reproduced 

 in fig. 380. In older stems of this species the leaf-bases are 

 exfoUated and the stem is covered with wrinkled and fissured 

 cork ; but in Cycas revoluta the leaf-bases are even more persistent. 

 The columnar but relatively stout stems of Encephalartos (figs. 

 379, 382, 386, A) and Ceratozamia are similarly encased in a 

 covering of petiole-bases, but in these genera the difierences 

 between foHage-leaves and bud-scales is much less obvious and 

 there is no zonal alternation. On the stems of Macrozamia the 

 rhomboidal leaf-bases are more uniform in size and there are no 

 scale-leaves. The tall and often palm-like stems of Microcycas 



' Hooker, J. D. (91) A. p. 98 (footnote). a Pearson (06). 



' Prof, de Vries kindly informed me in a letter that this estimate is not to be 

 regarded as anything more than a rough guess. 

 * Stopes (10). 



